From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wj0-f195.google.com (mail-wj0-f195.google.com [209.85.210.195]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3tNw1f4LJczDvh8 for ; Wed, 23 Nov 2016 19:07:50 +1100 (AEDT) Received: by mail-wj0-f195.google.com with SMTP id jb2so435226wjb.3 for ; Wed, 23 Nov 2016 00:07:50 -0800 (PST) Date: Wed, 23 Nov 2016 09:07:45 +0100 From: Michal Hocko To: Balbir Singh Cc: linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, Tejun Heo , Andrew Morton , Johannes Weiner , Vladimir Davydov Subject: Re: [mm v2 0/3] Support memory cgroup hotplug Message-ID: <20161123080744.GG2864@dhcp22.suse.cz> References: <1479875814-11938-1-git-send-email-bsingharora@gmail.com> <20161123072543.GD2864@dhcp22.suse.cz> <342ebcca-b54c-4bc6-906b-653042caae06@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <342ebcca-b54c-4bc6-906b-653042caae06@gmail.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Wed 23-11-16 18:50:42, Balbir Singh wrote: > > > On 23/11/16 18:25, Michal Hocko wrote: > > On Wed 23-11-16 15:36:51, Balbir Singh wrote: > >> In the absence of hotplug we use extra memory proportional to > >> (possible_nodes - online_nodes) * number_of_cgroups. PPC64 has a patch > >> to disable large consumption with large number of cgroups. This patch > >> adds hotplug support to memory cgroups and reverts the commit that > >> limited possible nodes to online nodes. > > > > Balbir, > > I have asked this in the previous version but there still seems to be a > > lack of information of _why_ do we want this, _how_ much do we save on > > the memory overhead on most systems and _why_ the additional complexity > > is really worth it. Please make sure to add all this in the cover > > letter. > > > > The data is in the patch referred to in patch 3. The order of waste was > 200MB for 400 cgroup directories enough for us to restrict possible_map > to online_map. These patches allow us to have a larger possible map and > allow onlining nodes not in the online_map, which is currently a restriction > on ppc64. How common is to have possible_map >> online_map? If this is ppc64 then what is the downside of keeping the current restriction instead? > A typical system that I use has about 100-150 directories, depending on the > number of users/docker instances/configuration/virtual machines. These numbers > will only grow as we pack more of these instances on them. > > From a complexity view point, the patches are quite straight forward. Well, I would like to hear more about that. {get,put}_online_memory at random places doesn't sound all that straightforward to me. -- Michal Hocko SUSE Labs From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f71.google.com (mail-wm0-f71.google.com [74.125.82.71]) by kanga.kvack.org (Postfix) with ESMTP id 52B8F6B0069 for ; Wed, 23 Nov 2016 03:07:48 -0500 (EST) Received: by mail-wm0-f71.google.com with SMTP id u144so3536896wmu.1 for ; Wed, 23 Nov 2016 00:07:48 -0800 (PST) Received: from mail-wj0-f194.google.com (mail-wj0-f194.google.com. [209.85.210.194]) by mx.google.com with ESMTPS id d128si1271611wmf.100.2016.11.23.00.07.46 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 23 Nov 2016 00:07:47 -0800 (PST) Received: by mail-wj0-f194.google.com with SMTP id f8so438923wje.2 for ; Wed, 23 Nov 2016 00:07:46 -0800 (PST) Date: Wed, 23 Nov 2016 09:07:45 +0100 From: Michal Hocko Subject: Re: [mm v2 0/3] Support memory cgroup hotplug Message-ID: <20161123080744.GG2864@dhcp22.suse.cz> References: <1479875814-11938-1-git-send-email-bsingharora@gmail.com> <20161123072543.GD2864@dhcp22.suse.cz> <342ebcca-b54c-4bc6-906b-653042caae06@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <342ebcca-b54c-4bc6-906b-653042caae06@gmail.com> Sender: owner-linux-mm@kvack.org List-ID: To: Balbir Singh Cc: linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, Tejun Heo , Andrew Morton , Johannes Weiner , Vladimir Davydov On Wed 23-11-16 18:50:42, Balbir Singh wrote: > > > On 23/11/16 18:25, Michal Hocko wrote: > > On Wed 23-11-16 15:36:51, Balbir Singh wrote: > >> In the absence of hotplug we use extra memory proportional to > >> (possible_nodes - online_nodes) * number_of_cgroups. PPC64 has a patch > >> to disable large consumption with large number of cgroups. This patch > >> adds hotplug support to memory cgroups and reverts the commit that > >> limited possible nodes to online nodes. > > > > Balbir, > > I have asked this in the previous version but there still seems to be a > > lack of information of _why_ do we want this, _how_ much do we save on > > the memory overhead on most systems and _why_ the additional complexity > > is really worth it. Please make sure to add all this in the cover > > letter. > > > > The data is in the patch referred to in patch 3. The order of waste was > 200MB for 400 cgroup directories enough for us to restrict possible_map > to online_map. These patches allow us to have a larger possible map and > allow onlining nodes not in the online_map, which is currently a restriction > on ppc64. How common is to have possible_map >> online_map? If this is ppc64 then what is the downside of keeping the current restriction instead? > A typical system that I use has about 100-150 directories, depending on the > number of users/docker instances/configuration/virtual machines. These numbers > will only grow as we pack more of these instances on them. > > From a complexity view point, the patches are quite straight forward. Well, I would like to hear more about that. {get,put}_online_memory at random places doesn't sound all that straightforward to me. -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org